This invention pertains to an improved-safety orthodontic mouth-bow/face-bow mechanism, and more particularly to such a mechanism wherein the mouth-bow and face-bow portions are separable with spring pressure which is developed in the mechanism continually urging these two portions apart when the latter are operatively interengaged.
Dental malocclusions are frequently treated by applying tractive force to the affected teeth by means of "braces". This type of installation generally involves the application of molar bands and an associated buccal tube to the patient's rear teeth, with or without the addition of an arch wire to provide proper tooth alignment.
Tractive force is transmitted to the molars by means of a mouth-bow/face-bow mechanism, which is attached to an elastic head or neck band. Typically, though not in all instances, the mouth-bow/face-bow mechanism employed is a unitary structure where the mouth-bow and face-bow portions are inseparable.
Generally, patients who are treated for dental malocclusions are preteen or teenage individuals. Some are required to wear a face-bow/mouth-bow mechanism, and an associated elastic head or neck band, on a time-extensive basis. As a consequence, such patients frequently come in contact with their peers, who have on occasion in the past, either intentionally or accidentally, pulled a face-bow away from patients' faces and released their grip on the device. This act results in an extremely dangerous condition where the mouth-bow and face-bow portions either cannot separate, or if they are designed to separate, become stuck together so that they don't separate. Such a condition is one where the sharp ends of the mouth-bow are substantially aligned with a patient's eyes as the mouth bow snaps back toward the patient's face, and there have been numerous reported accidents where patients have lost their eyesight as the result of just such an incident.
Safety mechanisms of various types have been proposed to eliminate the hazard to a patient caused by a mouth-bow striking the face. One such device is a safety head gear assembly, which separates at a point of connection between a face-bow and head band upon being pulled, thereby eliminating the tractive force which brings the mouth-bow back into a patient's face. Another approach has been to make the mouth-bow and face-bow portions separable under tension so that a pull on a face-bow does not transmit a pull on a mouth-bow. However, while such apparatus has been useful, it has not always proven to be foolproof and there is, consequently, a continual interest in providing further safety protection.
A general object of the present invention, accordingly, is to provide a unique safety-release face-bow/mouth-bow combination, which will transmit the desired range of orthodontic tractive tension and which will positively separate, face-bow from mouth-bow, when such tension is released.
According to a preferred embodiment of the invention the proposed positive release mechanism includes two compression-transmission connectors, one mounted on a face-bow and the other mounted on a mouth-bow, which connectors coact with each other to provide appropriate compression transmission during patient use. One connector carries a spring parting means which acts forceably and positively to separate the two connectors when compression transmission is relaxed. In the preferred embodiment, the spring parting means is carried on the connector associated with the face-bow. It takes the form of an elastomer band which surrounds the face-bow connector perpendicular to what might be thought of as the plane of the face-bow. The face-bow connector has an open-ended socket which freely receives the mouth-bow connector. The band has a stretch extending across the face-bow socket which is forced into the socket when the face-bow and mouth-bow connectors are operatively connected.
In another embodiment of the invention, the spring parting means is also an elastomer band which, in this case, stretches around the face-bow connector, and across such an open-ended socket, generally in the plane of the connector.
Further embodiments are described herein where the spring parting means takes the form of either a coil or leaf spring.
Considering the preferred embodiment of the invention in normal usage, the mouth-bow is inserted into buccal tubes conventionally mounted on a patient's teeth, the mouth-bow and face-bow connectors are connected, and the face-bow is connected to a head-band assembly of the type which provides the required compression transmission. Tension in the head-band assembly is transmitted to the face-bow, through the connectors, to the mouth-bow and ultimately to the teeth undergoing treatment. If pressure on the face-bow is released, the elastomer band positively forces the connectors apart, thereby promoting retention of the mouth-bow in the patient's mouth and eliminating the possibility that the mouth-bow will snap back into either the patient's mouth or face causing injury.